Double-acting fluid pressure pump



May 6, 1958 B. w. ROBINSON ET AL 2,833,220

DOUBLE-ACTING FLUID PRESSURE PUMP Filed oct. a. 1954 FIG.4

1N VEN TORS BILLY W. ROBINSON BY ROBERT C. CRUZAN DOYLE E. WlLOOX ATTORNEY United States Patent C DOUBLE-ACTING FLUID PRESSURE PUMP Billy W. Robinson, Santa Ana, Robert C. Cruzan. Eeib flower, and Doyle E. Wilcox, Puente, Calif., assignors to North American Aviation, Inc.

Application October 8, 1954, Serial No. 461,208

1 Claim. (Cl. M3U-53) This invention relates to subminiature electromagnetically operated double-acting, reciprocating uid pressure pumps and more particularly pertains to the above type of pump to be used to pump Huids at pressures which will not fluctuate more than one pound per square inch.

ln pumping a lubricant to fluid type bearings, special problems are encountered. Where the bearings are of the fluid type or where the instrument is actually floated in the fluid, a special type of lubricant such as Fluorolube-FS or tetrabromoethane is often used. Fluorolube-FS, a product of the Hooker Electrochemical Company is a compound of a series of polymers of triiluorochloroethylene and has a specific gravity of about 1.88, twice that of the average lubricating lluid. These fluids are satisfactory for the above purpose, and it is their heavy weight plus lubrication properties which make them especially desirable. They have the necessary low vapor pressure which prevents their vaporizing at higher temperatures. However, any system which uses these fluids must be closed to the atmosphere because of their aliinity for absorbing gases, especially air. In addition, as the pumps presented here are used to circulate these lubricants in certain precision instruments and to llotation gyroscopes in airborn autonavigation systems which may operate in raried atmospheres, the system must be closed to maintain a nearly constant sink pressure. Further, in such sys tems space and weight limitations are always problems. The pump disclosed herein has been conceived to solve the` above problems. Requirements of this pumps are to circulate 25 to 50 cc. of uid per minute with pressure from to 50 p. s. i. g. and with a iiuctuation of n-ot more than 1 p. s. i. It may be electrically operated by means of 2128 volt D. C. circuit through an external switching means which alternately energizes each of two separate solenoid coils so as to operate the combined plunger and cores iirst in one direction and then in the other. The plunger-core is composed of two metallic sections, such as soft iron, and has a spacer disc of nonmagnetic metal which is joined to the two sections by a means, such as silver solder, to form one solid, cylindrical plunger. The coils are arranged so that when one is energized, magnetic lines of force are passed through one of the soft iron sections, causing the plunger to move in one direction. When the other coil is energized, magnetic lines of force pass through the other sott iron section causing the plunger to move in the other direction. Each movement of the plunger, which is double-acting, takes a suction at one end and causes discharge of the uid under pressure at the other. The fluid is pumped through a surge chamber on the discharge line and because cleanuid must be delivered to the hydrodynamic bearings, a'tlter of akmaterial such as sintered metal or glass wool surrounded by wire screen is provided.

This invention contemplates the provision of an economically constructed subrniniature, lightweight iluid pump adapted to deliver a constant volume rate of ilow at a pressure with fluctuations not to exceed l p. s. i.

Therefore an object of this invention is to provide an Mice improved pump for circulation of heavy iiuids at a constant volume rate of flow and at a pressure with fluctuations not to exceed l p. s. i.

A principal object of this invention to provide an proved pump suited for use in a closed system where no external leakage is permissible.

lt is another object of this invention to provide an economical, light-weight subminiature, electu'cally operated, double-acting, reciprocating pump.

Itis still another object of this invention to provide a small pump having a built-in lter and built-in surge chamber.

it is a further object of this invention to provide a double-acting pump having simple pump-pressure actuated, one direction closing, springless, unattached disc valves which are reliable, quick acting, and are easy to fabricate.

Itis another object of this invention to provide a pump having two solenoid cores as sections of the plunger so that when either of the solenoid coils is energized the plunger will move in a direction which is dependent upon the coil which is energized.

Another object of this invention is to provide a pump in which part of the pull on the plunger is induced by electromagnetic force and the balance of the net force acting on the plunger is delivered by compression springs which counteract the large electromagnetic force at the end of the plunger stroke and add to the electromagnetic forces at the beginning of the stroke.

Further objects and features of invention will become apparent from the following description, in which Fig. l is a cross-sectional View of the `type of pump used Where space is greatly limited;

Fig. 2 is a cross-sectional view of the type of pump used where the space limitation is not as great as that requiring the type shown in Fig. 1;

Fig. 3 is a cross-sectional view of a relieved-seat typ disc valve assembly;

Fig. 4 shows a plan view of a valve along the lines 4-4 of Fig. 3;

And Fig. 5 shows a cross-sectional View of a recessedvalve type disc valve assembly.

Referring to Fig. l, the pump comprises a body 1 in which a cylinder 5 is litted. Cylinder 5 consists of two sections 5a and 5b which are joined by a spacer ring 4 to form one smooth internal surface. Sections 5a and 5b are of non-magnetic material, such as non-magnetic stainless steel, and spacer ring 4 is of magnetic metal, such as soft iron. Around cylinder sections 5a and 5b are wound two solenoid coils 2 and 3, respectively. Cylindrical plunger 6 is inserted in cylinder 5 with a clearance from 0.0002 to 0.0005". Plunger 6 consists of two sections 6a and 6b of magnetic metal, such as soft iron, with relatively non-magnetic spacer disc 7, of material such as stainless steel, attached therebetween. Valve housings 8a and 8b are adjacent to one end of cylinder S and valve housings 9a and 9b are adjacent to the other end. Valve housings 8b and 9a are also of magnetic metal, such as soft iron. Inlet valve 10 and outlet valve 12 are located in the housings Sa and 8b and inlet valve 11 and outlet valve 13 are located in the housings 9a and 9b. Suction line 14 allows iiuid to flow through inlet valves 10 and 11 into cylinder S. Exhaust line 15 permits ow of fluid from cylinder 5 through outlet valves 12 and 13 to surge chamber 16 where fluid passes through filter 17 to discharge line 15a. Floating inside of surge chamber 16 and within filter 17 is a metal or rubber', hollow, sealed bellows 18. A hollow rubber ball may be used in the surge chamber in place of the bellows. Compression springs 19 and 20 are located abutting the ends of plunger 6.

The pump is caused to operate by energizing solenoid coils 2 and 3 alternately and consecutively through an external automatic switching means. Thus, when coil 2 is energized, the path of the magnetic flux created flows through magnetic spacer ring 4 to section 6a of plunger 6 and thence, through valve housing db. Movement of the flux through the above path causes plunger 6 to move toward valves 16 and 12 and the pumping action is started. Non-magnetic spacer disc 7 limits the path of the magnetic flux in plunger 6 to section 6a and thus materially improves the eiciency of the pump. In a like manner, when coil 3 is energized, plunger 6 moves toward valves 11 and 13 and spacer disc 7 limits flow of the magnetic flux from coil 3 to section 6b of plunger 6. When plunger 6 moves toward valves 1i) and 12, :as the result of the iiux from coil 2, a partial vacuum is created in cylinder in the vicinity of inlet valve 11 thereby causing it to open, -allowing tiuid to flow through inlet line i4 into cylinder S between plunger section 6b and valve housing 9a. At the same time outlet valve 13 is forced closed. At the -other end of plunger 6 the pressure created causes inlet valve to close and outlet valve l?. to open. Fluid in cylinder 5 in the vicinity of outlet valve 12 will be caused to flow through exhaust line 15 into surge chamber 16, through lter 17 and out into the system through discharge line 15a. This completes the rst half of the pumping cycle and the automatic alternating switch then operates to de-energize coil 2 and to energize coil 3. The lux created by coil 3 causes plunger 6 to travel toward valves 11 and 13 and the operation of each of the four valves is reversed. Fluid thus llows through valve 10 into cylinder 5 between plunger section 6a and valve housing 8b, and the fluid previously admitted at the lother end of cylinder 5 is exhausted through valve 13 into line 15. This completes one cycle of the pump.

Fig. 2 shows essentially the same pump as illustrated in Fig. l and is used where the space limitations are not as great. One difference shown, not relative to space, is the employment of ball valves 40, 42, 41 and 43. They are of material such as nylon and seal against beveled seats a, 42a, 41a, and 43o. They, like the discs, are unattached and seal only in one direction, as explained in the description of Fig. 4. This pump allows a larger lter 47 which permits finer filtering action without increasing drop of iluid pressure "across the lter, and a larger surge chamber 46 which allows better regulation of discharge pressures. The filter is of the same type as that above, either of glass wool or sintered metal, and it collects contaminants from the entire system.

Referring to Figs. l and 2, in order to limit the pressure uctuations to l p. s. i., it is necessary to control the velocity of plungers 6 and 36, respectively, through the entire stroke as well as to have a properly designed surge chamber. A substantially constant plunger velocity may be achieved by regulating the magnitude of current, which energizes coils 2 and 3, and 32 and 33, so that it is inversely proportional to the square of the length of the air gap between plunger 6 and cylinder 5, and plunger 36 and cylinder 35, respectively. In design of bellows 18 :and 48 and surge chambers 16 and 46, it has been found by test that the most steady output pressures are achieved when the pressure in the bellows is the same as that of the outgoing fluid. In addition, because of th varying temperatures at which the pump must operate, the surge chamber must be designed to allow for expansion and contraction of the uid within the closed system. In the event that the plunger is given a sudden surge or if the fluid is caused -to expand, Huid will be forced against the bellows causing it to contract. When the movement of the plunger returns to its normal velocity or the fluid returns to its initial volume, the bellows will return to its normal size.

Referring again to Figs. l and 2, in order to make the pump operate more efficiently, compression springs 19 and 20, and 49 and 59 may be inserted in counter-bored openings 19a and 29a, and 49a and Stia, respectively. The outer ends of each of the springs are seated against springs tend to equalize the net pull on the plungerA throuhgout the entire stroke. Part of the pull is introduced by electromagnetic attractions and the balance of the net force acting on the plunger is delivered by the springs.

In order to make the pump as small as possible, the movement of plungers 6 and 36 is limited to the length of cylinders 5 and 35, respectively. Compactness is further enhanced by combining cores 6a and 6b of coils 2 land 3, and cores 36a and 3617 of coils 32 and 33 into the single plungers 6 and 36, respectively.

Because of the pressure which must be delivered, the length of stroke and air gap in the present pump has been held to 0.040". This short stroke requires from 600 to 800 pumping strokes per minute. Therefore, a fast acting positive valve is needed which is light and highly responsive to pressures. Several types have been developed for use.

Referring to Fig. 3, a thin disc type of valve has been employed in the type of pump shown in Fig. l. As the opening of the valve depends upon the differential force acting on disc 52, that is, pressure in passage 51 times the disc area exposed to passage 51 minus the pressure in chamber 55 times the exposed disc area in chamber 55, the valve housing 57 has been relieved at 53, leaving a small surface seating area 54. Thus, the dierential force necessary to open the valve has been greatly reduced. Seating of the disc 52 and closing of the valve is accomplished by an impulse imparted to the disc by the change in momentum of the incoming uid as it strikes dise 52 from passage 56. This type of valve is one that is highly responsive to pressures and obviates the need of any spring or other disc attachment.

Referring to Fig. 3 and to Fig. 4 which shows a view along the lines 4 4 of Fig. 3, to prevent the valve disc 52 from seating in both directions, groove 58 is cut deeper than chamber 5S. When lluid is owing from passage 51 through the open valve into passage 56, it will ow past disc 52 through groove 58 into passage 56.

Referring to Fig. 5, another type of valve is shown which operates on a principle similar to that in Fig. 3, except that disc 62 is recessed at 63 to `leave a small 4seat contact area 64. This is in lieu of relieving the valve housing as indicated in Fig.'3. The valve also employs the same cutout groove 68, shown in Figs. 3 and 4 as 58.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by yway of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claim.

We claim:

A double-acting, reciprocating pump comprising a closed-ended, cylindrical plunger; said plunger comprising rst and second magnetic sections having a nonmagnetic disc therebetween, said disc being of predetermined thickness, a cylinder having non-magnetic sections surrounding -said plunger and forming pump chambers with the plunger at either end of the cylinder, electromagnetic means to reciprocate said plunger within said cylinder, said last means including a iirst solenoid coil surrounding said cylinder and said first section of said plunger, a second solenoid coil surrounding said cylinder and said second section of said plunger, and a magnetic spacer ring of predetermined thickness which is substantially `greater than said disc thickness. said coils being separated by said magnetic spacer ring which is tted in said cylinder and which forms a part of the internal face thereof, said ring abutting said non-'magnetic disc, an inlet f port means and an outlet port means `at either end of said cylinder for receiving and exhausting fluid into and from the pump chambers formed at either end of the cylinder.

(References on following page) References Cited in thc le of this patent UNITED STATES PATENTS Holcombe et al. Dec. 28, 1880 Van Depoele Oct. 13, 1891 -Schoolfield et a1. Dec. 8, 1914 Brown Sept. 18, 1928 6 Guinn et al Mar. 6, 1934 Dickey Mar. 30, 1954 Basilewsky Sept. 28, 1954 FOREIGN PATENTS Italy Dec. 15, 1939 Germany Oct. 23, 1952 

